In face-down mounting of a semiconductor chip (semiconductor element) on a substrate, an undesirable gap is formed between the substrate and the semiconductor chip. The gap must be filled with an insulating material called underfill. Thermosetting resins such as epoxy resins have been widely used as materials for the underfill (Patent Document 1).
[Patent Document 1] Japanese Unexamined Patent Application Publication No. H11-233571